Detailed multidisciplinary monitoring reveals pre- and co-eruptive signals at Nyamulagira volcano (North Kivu, Democratic Republic of Congo)

This paper presents a thorough description of Nyamulagira's January 2010 volcanic eruption (North Kivu, Democratic Republic of Congo), based on a combination of field observations, ground-based and space-borne data. It is the first eruption in the Virunga Volcanic Province that can be described based on the combination of several modern sensors and techniques. The 2010 eruption lasted 26 days and, according to our estimate, emitted ~45,52 ? 106 m³ of lava. Field observations allowed the subdivision of the event into 4 eruptive phases delimited by major changes in effusive activity. These phases are consistent with those described by Pouclet (1976) for historical eruptions of Nyamulagira. Co-eruptive signals from ground deformation, seismicity, SO2 and radiated thermal energy correlate with the eruptive phases. Clear unambiguous pre-eruptive ground deformations are observed about 3 weeks prior the lava outburst. They coincide with a small, though clear increase of the short period seismicity. These precursors contrast with the only previously precursory signal recognized so far in the Virunga, which was the increase of tremors and long period seismicity and which were only detected less than two hours prior the 2010 eruption.

As far as we know, the present paper is the most detailed picture of a typical flank eruption of this volcano. It provides valuable tool for revisiting former - mostly qualitative - descriptions of historical Nyamulagira eruptions that occurred during the colonial times. In a companion paper (Smets et al., Bull. Volcanol., in this issue), we interpret eruption mechanisms of Nyamulagira by studying inter-, pre- and co-eruptive signals of the 2010 eruption that were recorded by the seismic network of the Goma Volcano Observatory, Satellite Radar Interferometry (InSAR) and thermal imagery.